In the mid-1990s, astronomers made history when they began to find planets orbiting stars in the Milky Way. More than eight hundred planets have been found since then, yet none of them is anything like Earth and none could support life. Now, armed with more powerful technology, planet hunters are racing to find a true twin of Earth. Science writer Michael Lemonick has unique access to these exoplaneteers, as they call themselves, and ''Mirror Earth'' unveils their passionate quest. Unlike competitors in other races, Geoff Marcy, Bill Borucki, David Charbonneau, Sara Seager, and others actually consult and cooperate with one another. But only one will be the first to find Earth's twin. ''Mirror Earth ''tells the story of their competition.